Presently available imaging diagnostic apparatuses for capturing diagnostic images of patients include CT (Computed Tomography) scanners, MRI (Magnetic Resonance Imaging) apparatuses, PET (Positron Emission Tomography) apparatuses, ultrasonic diagnostic apparatuses, CT angiography apparatuses, MRA (MR angiography) apparatuses and the like. When the abovementioned imaging diagnostic apparatuses are used, a chemical solution such as a contrast medium or physiological saline may be injected into a patient. Chemical solution injectors for automatically performing the injection have been put into practical use.
Such a chemical solution injector has a piston driving mechanism formed of a driving motor, a slider mechanism and the like, for example. A chemical solution syringe is removably mounted on the injector. The chemical solution syringe typically includes a cylinder member and a piston member slidably inserted in the cylinder member. There are a pre-filled type and a refill type in the chemical solution syringe.
The chemical solution syringe of the pre-filled type includes a cylinder member filled with a chemical solution and is wholly sealed by a packing material for shipment. The chemical solution syringe of the refill type includes a cylinder member which can be filled with a desired chemical solution by a user. For simplicity, the following description will be made assuming that the chemical solution syringe of the pre-filled type is used.
When the chemical solution in the chemical solution syringe of the abovementioned type is injected into a patient, an operator prepares a chemical solution syringe containing an appropriate chemical solution and takes out the chemical solution syringe from the packing material. The operator connects the chemical solution syringe to a patient through an extension tube and mounts the chemical solution syringe on a chemical solution injector. The chemical solution injector moves the piston member relative to the cylinder member in response to predetermined operation to inject the chemical solution into the patient from the chemical solution syringe.
The operator determines the rate at which the chemical solution is injected and the total quantity of the chemical solution to be injected in view of the type of the chemical solution and the like, and enters data representing the rate and total quantity into the chemical solution injector. The chemical solution injector injects the chemical solution into the patient based on the entered data. For example, when a contrast medium is injected as the chemical solution, the image contrast of the patient is changed to allow the imaging diagnostic apparatus to capture a favorable diagnostic image of the patient.
The chemical solution injector for the abovementioned CT angiography apparatus injects a contrast medium with a high viscosity into a blood vessel, so that the piston member of the chemical solution syringe is pressed into the cylinder member at an extremely high pressure. The high pressure is likely to break the cylinder member if the chemical solution syringe is directly mounted on the chemical solution injector for use. To avoid this, in a mechanical system for the CT angiography apparatus, a cylinder adapter may be put on the cylinder member of the chemical solution syringe and used to hold the chemical solution syringe on the chemical solution injector (see, for example, non-patent document 1 below).
Non-patent document 1: “Angiography Contrast Medium Injector in product guides of Nemoto Kyorindo Co., Ltd” (retrieved in Jul. 14, 2004) (URL:http://www.nemoto-do.co.jp/seihin_ang.mr.html#120top)
In the chemical solution injector of the abovementioned type, since the cylinder member of the chemical solution syringe is held by the cylinder adapter, the piston member can be pressed into that cylinder member at a high pressure. The abovementioned cylinder adapter is formed of polycarbonate or polyamide 12 having a predetermined thickness or less since the interior of the chemical solution syringe needs to be visually checked when the cylinder adapter is used.
Thus, the abovementioned cylinder adapter cannot be formed as a permanently usable part but as a consumable part which needs replacement after a predetermined number of uses. However, it is difficult to control the number of uses of the cylinder adapter in a medical facility such as a hospital, and the cylinder adapter may be broken after it is used beyond the consumption limit. To prevent this, cylinder adapters are replaced once in a predetermined time period such as once in a year in some medical facilities, but in this case, a cylinder adapter which can still be used a number of times before the consumption limit may be replaced.
Some chemical solution injectors for the MRI apparatus employ a secondary battery as a power source. The secondary battery is also formed as a consumable part which requires replacement after a predetermined number of uses. However, it is also difficult to control the number of uses of the secondary battery in a medical facility such as a hospital, resulting in replacement of a secondary battery after it is used beyond the consumption limit or a secondary battery which can still be used a number of times before the consumption limit.